brightness

noun

bright·​ness ˈbrīt-nəs 

1

a

: the quality or state of being bright

also : an instance of such a quality or state

b

: luminance

2

: the attribute of light-source colors by which emitted light is ordered continuously from light to dark in correlation with its intensity compare hue sense 2c, lightness entry 1 sense 2a, saturation sense 4

Synonyms

• brilliancy
• brilliance
• lightness
• illumination
• luminosity

Examples of brightness in a Sentence

the brightness of the sunshine made me squint after an afternoon spent in a darkened movie theater

Recent Examples on the Web

Boox has added a frontlight to the display that can vary both its brightness and its color warmth. —Ewan Spence, Forbes.com, 13 Sep. 2025

The iPhone 16e is a little dimmer, with a typical brightness of 800 nits and a peak of 1,200 nits. —PC Magazine, 12 Sep. 2025

Its low surface brightness and lack of clear polarization also complicate the picture. —Kaif Shaikh, Interesting Engineering, 11 Sep. 2025

The brightness of quasars should make these supermassive black holes pretty conspicuous even at vast distances, and indeed, the team behind the new research used the Subaru Telescope to discover over 200 quasars. —Robert Lea, Space.com, 11 Sep. 2025

Word History

First Known Use

before the 12th century, in the meaning defined at sense 1a

Rhymes for brightness

• lightness
• rightness
• tightness
• whiteness
• politeness
• uprightness

Medical Definition

brightness

noun

bright·​ness ˈbrīt-nəs 

: the one of the three psychological dimensions of color perception by which visual stimuli are ordered continuously from light to dark and which is correlated with light intensity compare hue, saturation sense 4a